PHPTAL is licensed under LGPL (v2.1 or later).

The licence does not "infect" other software you use with PHPTAL, so it's safe for commercial (closed, for-profit) use in PHP applications.

• You can use it in commercial applications.

• Your website and your templates remain your property and are unaffected by the license.

• You can redistribute PHPTAL with applications, even if they're not free/open-source.

• You can charge money for PHPTAL customisations and you can even sell modified versions of PHPTAL (although you cannot forbid redistribution).

You only have obligations if you redistribute PHPTAL (give PHPTAL's source code to others). Sending of PHPTAL-generated HTML from a server doesn't count as redistribution.

• If you modify and redistribute PHPTAL, then your modifications of PHPTAL's code (and only PHPTAL's code) become LGPL-licensed.
  However, if you always keep PHPTAL only on your server, then you're allowed to keep your modifications secret.

• If you redistribute your application to others with PHPTAL built-in, it must be possible to modify PHPTAL part of the application. If you use copy protection (encryption/obfuscation of PHP files), don't apply it to PHPTAL files.

• Don't remove license (COPYING file) from PHPTAL copies you give to others.

IANAL. This page is only non-legally-binding summary.