Simple choice. If you do not like the fact that Comodo, as a commercial entity, choose to not make their source code publicly available, then don't use their products.
A quick google revealed a listing of 123 currently available OTFE products. Of these, only 9 have made their source code available. That leaves 114 that have chosen to be secure in how they publicly define their software.
You mentioned two very good products in your post - TrueCrypt and FreeOTFE. Both are excellent products and worthy of your full consideration.
Not everything "commercial in confidence" is bad. Similarly, not everything open is good.

Ewen :-)