Are you planing to open the code at all ?
Yes, I am still planing this. However, I really want to do a deep review concerning the access control and security related issues. I also looked in all security issues published for Drupal 7 (older versions do not count). Here are my considerations:
SA-CORE-2011-001
http://drupal.org/node/11687561 critical Reflected cross site scripting vulnerability in error handler: not critical if following the guideline for productive websites. Effects cryptocoin modules.
1 Cross site scripting vulnerability in Color module: Requires higher rights "Administer themes" Might effect cryptocoin modules
1 Bypass access to private files: Does not effect cryptocoin modules
SA-CORE-2011-002
http://drupal.org/node/12045821 Highly critical: Access bypass in node listings. Requires additional modules to be critical. Does not effect cryptocoin modules
SA-CORE-2011-003
http://drupal.org/node/12315101 less critical: download of shared files without permissions by guessing the file name. Does not effect cryptocoin modules
SA-CORE-2012-001
http://drupal.org/node/14250841 denial of service in aggregator module. Does not effect cryptocoin modules
1 issue in OpenID also effects Drupal if this module is enabled (view user information), might be an issue
1 download of shared files without permissions in combination with other not core modules. Does not effect cryptocoin modules
SA-CORE-2012-002
http://drupal.org/node/1557938critical
1 denial of service: requires higher right: "post comments" or "Forum topic: Create new content". Does not effect cryptocoin modules
1 Unvalidated form redirect: requires social engineering. Effects cryptocoin modules (of course it is social engineering)
1 Access bypass - forum listing: showing last unpublished node, even if user has no access. Does not effect cryptocoin modules
1 Access bypass - private images: view of private images without permissions. Does not effect cryptocoin modules
1 Access bypass - content administration: requires higher rights "Access the content overview page" and additional modules. Does not effect cryptocoin modules
For 4 of the reported issues the hacker may have access to the user account, but not to the administration interface. The attacker cannot control the daemon!
Concerning the user account, as said, I am think of 2 factor authorization. If an attacker can access the user account, he still cannot send the coins out.
I do not consider other modules which could cause a risk. It is like saying windows in insecure, because Adobe Acrobat has a security issue. Drupal's core is reasonable hard to attack I think.