I am the author of Keepmark, but the sales process is handled by FastSpring. The company charges a certain fee for each sale, but it's also a great convenience for me because I don't have to deal with detecting the country of sale of the service and accounting for VAT on my own.
I'm creating this software as registered business activity. My company's data is:
Codeset Tomasz Chudyk
40-142 Katowice, Poland
NIP/VAT: PL 5482434661