1st of all, Modafinil IS an antidepressant. Multiple studies exist in the literature to back this claim up, as well as a large body of case studies and anecdotal evidence.
2nd of all, the title of this thread should be changed; it seems to be that the OP wanted to know if there was an interaction between modafinil and DMT+Harmalas, so it logically follows that the title should reflect that.
and 3rd of all...I tried it out! I am currently prescribed 200mg/day R-Modafinil, and have been taking this medication for several months. Today, I became curious as to how these two guys would play out, and upon finding almost nothing regarding this interaction, gave it a try myself.
4 hours after taking the R-Modafinil, I ventured out into the forest with a one-hitter packed up to the brim with 50mg of a 1:1:.3 DMT:Herb Harmala changa, found my launch-log, propped myself lying supine along the fallen, mossy tree-trunk, cleared the bowl in one hit...
...And the rest was simply
Suoicodilaipxecitsiligarfilacrepus 
I found that R-Modafinil enhanced the afterglow of changa (it still hasn't stopped, even 3 hours after taking that first hit) and that the changa seemed to add to the mood boost, sense of well-being, and similar such typical antidepressant effects. I noticed no negative, harmful or serious side effects resulting from combining these two drugs. With regards to intensity, I am afraid the jury is still out on that question. The trip was beautifully intense, albeit a little step away from a full on breakthrough which 90mg gave me when i wasnt on modafinil. I noticed that, while on modafinil, the "carrier wave" effect (AKA the 'flash' brought about by freebase DMT in which the user is shot straight out of a cannon uncontrollably into hyperspace) is elicited by harmalas. When I was not taking R-Modafinil, I noticed that changa induced a more gradual immersion into the depths of hyperspace, with a slightly prolonged come-up stage which wasn't disorienting. When I smoalked changa while on modafinil, I cleared the entire on hitter in one hit and noticed a very strong popping sound and then WHOOOSH I was there all over again straight shot out deep deep into the dark depths of our collective consciousness.
While it did enhance and prolong the afterglow, R-Modafinil had no impact on the duration of action. As per the norm, I was unable to check the time until 42 minutes had passed, at which point the primary hallucinogenic effects were completely gone while a stronger sense of euphoria/well-being was noticed. I felt very happy and laughed uncontrollably for a few minutes after realizing I had been hypersurfing for almost an hour off of only one hit. I felt content and blissed-out in the angelic afterglow. Social Anxiety was markedly reduced--multiple conversations were had on the walk home. While talking, I noticed that I seemed to be much more involved in the conversation and emotionally sensitive/emotive than usual. I was better able to adapt to body language and control my own, positivity oozing out of my mouth. I was much more involved with what they had to say as well, and, through better-thought-out emotional expression, was able to recruit some potential future friends. That being said, I can say that my experience was extremely vivid and positive and that I will try this again in the near future.
Overall, I find this combination to be interesting and have only gotten positive things so far.
HOWEVER,
I strongly recommend that anyone else who attempts this combination take extreme caution. Everyone is different in an infinite multitude of ways and means.
What works for me might kill you. While I would be interested in others' experiences with this peculiar combination, I must warn any potential contributors to play it safe.
It should also be re-stated that I have not combined modafinil with neither ayahuasca or oral/sublingual harmalas, only with a minute amount of vaporized syrian rue extract. When smoalked, harmalas peak fast and leave fast. The pharmacokinetic profile of smoked harmalas is relatively unknown as far as I am aware, and I'd presume that, when smoked, harmalas would be excreted at a faster rate and have a shorter duration of action. This might mean that there would be less time to inflate serotonin levels to fatal levels, or that modafinil may not act on serotonin in a manner similar to MDMA/AMPH. Regardless of my speculatory shtick, It should be emphasized that I only smoalked harmalas while on modafinil and have never eaten harmalas while on it. I also highly doubt that the amount I smoalked would be enough to sufficiently inhibit MAO-A--there is pretty much no well-proven scientific theory which may explain why such small amounts of inhaled harmalas potentiate smoalked DMT in such a profound way.
In short, I would like to say that the combination was much moar than ecstatic than expected. I would like to hear from anyone else who has experience with this combination or could provide me with links to other webpages addressing this topic; however I must urge complete caution if you do decide to try this combination out; if you decide to try, start slow, take your time, and work your way up. Hyperspace isn't going anywhere anytime soon.
Selah,
-God
'"ALAS,"said the mouse, "the world is growing smaller every day. At the
beginning it was so big that I was afraid, I kept running and running, and I was glad
when at last I saw walls far away to the right and left, but these long walls have
narrowed so quickly that I am in the last chamber already, and there in the corner
stands the trap that I must run into." "You only need to change your direction," said
the cat, and ate it up.' --Franz Kafka