The message is clear:
You're trying to install or update to phpBB 3.3 but using php 5.x.
You're using Usbwebserver 8.6 or 8.6.1 but for phpBB3.3 you need UsbWebserver 8.6.2 with php 7.1
Spelling is freeware, which means you can use it for free.
On the other hand, it is not open source, which means you cannot change it or publish it in a modified form.