Hi:

When choosing which prefix to use, I would suggest against being too concerned with which obscure software project already uses it. ToscaWidgets is still in alpha according to their webpage, which hasn't been updated in ages. I don't mean to deride another project, but considering the high rate of failure of most OSS projects, unless it has a community inertia as large as or larger than Twisted's, I say every project for itself.

I would be tempted to use a prefix like tsf or twsf so there is a closer association to the Twisted Software Foundation, the entity that is the custodian of Twisted. I know little about trademark law (especially in the U.S) but I think there are benefits when the legal entity and the product/service share a name (trade name) Cheers, Andrew