Request to co-maintain a module

Issue Summary

Hi!
I'm use this module on several projects and have some troubles.

1) Module incompatible with PHP 5.3.
2) I had situation when Robokassa send duplicates POST requests several times and it's cause payment duplication. Money were added to accout twice.
3) Coding standards are missed.
4) Robox module should not to be installed without XML/Unserializer.php, to avoid fatal errors and warnings.
5) There is no posibility hook into pgapi_transaction_save to modify transaction object - $t in my custom modules (i. e. add bonus for big payment amount)

I want to become a module co-maintainer to fix this problems.