- Avoid using the PHP license. MIT, LGPL, New BSD etc are preferred ones
- The existing Number_Roman package already handles the Roman to Arabic conversion
- Package should be PHP 5+
- Put the code of your package directly viewable online
- Use func_get_args() to eliminate duplicate functions gcm(), gcm_mult() and so forth
- function names should be camelCase isPositive() vs is_positive()
I don't know what your date and conversion functions do, but they shouldn't be in the same package as an equation-related one.