Thanks, Newart. I will appreciate any suggestion about money transfer and what is common in Russia for payments.
OK, I will focus on TR-DOS, which is unknown to me. I welcome anyone willing to help me, and/or I can research by myself and release a TR-DOS version in a few months. By the way, I'm from Argentina, where there was a Speccy 48K clone only (CZ Spectrum), no original software, etc, maybe similar to the Russia scheme. But in any case, no disk units were built-in, I barely remember disk units sold separately and they were expensive, specially for my dad...
Thanks for your comments, I find them very helpful for improving games and service.
Ariel