I personally rehabilitated a historic building (house now used commercially) that generated credits in 2010, and is held under a single member LLC.
I rent part of the building for special events (a small side-business in which I do all the work), all through the LLC.
I have a few offices for rent. I am not a real estate professional, and this is my only property.

I also own a single member S-Crop and I pay rent to the LLC for some office space. I still show a loss, so its passive loss under the self-rental rules.
I'ts been recommended by a CPA that I rent substantially more of the building in order to show a profit (non-passive income under the self-rental rule), which would allow unlimited use of the tax credits - which is what I'm trying to verify.

I've seen IRS text stating that "credits are not limited on active projects" (i.e. "John is an architect" example in circumstances where RTC is not limited). see 22-3 in http://www.irs.gov/pub/irs-mssp/rehab.pdf

But I've read the Siddell v Commissioner case and it seems to contradict this, although that case is fairly complex but frequently cited.

see 22-4 in
http://www.irs.gov/pub/irs-mssp/rehab.pdf
and a really deep synopsis in:
SIDELL v. COMMISSIONER OF INTERNAL REVENUE, No. 00-1078., September 22, 2000 - US 1st Circuit | FindLaw

This is all very contradictory to me and admittedly way over my head.
I really need some help interpreting this and the IRS is shut down.