Wiktionary
donationware
n. (context Internet English) A variant of freeware that offers an option to its user to donate money to the program's author.
Wikipedia
Donationware
Donationware is a licensing model that supplies fully operational unrestricted software to the user and requests an optional donation be paid to the programmer or a third-party beneficiary (usually a non-profit). The amount of the donation may also be stipulated by the author, or it may be left to the discretion of the user, based on individual perceptions of the software's value. Since donationware comes fully operational (i.e. not crippleware/ Freemium) when payment is optional, it is a type of freeware.