1. how much is the best price available at this moment? Am I eligible for kind of discount?
See www.wordfast.net > Buy section.
2. do I have to pay regularly (say, two years) to renew my use of WF, like use of anti-virus software?
3. after purchase, do I have the right to upgrade WF for free or if not free, how do you charge for that?
See the Wordfast license agreement, linked from the Buy section or directly at:
4. I would like to have a version of WF capable of being operated with a network translators, like in a company, several translators can make input or output into the RM memory. Is there such a version?
This is part of Wordfast, the standard and the only version. Download, install, and test it. Without a license, Wordfast runs in demo mode, explained at:
5. do I have to pay in forex or pay in RMB?
You can pay through PayPal or Share-It. Share-It, a major ecommerce operator, accept credit card payments, bank wire transfers, cheques. You can switch the price to RMB on both payment sites, I believe.