The software comprising Apple Befunge proper is in the public domain, as
described in the following Unlicense:

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This is free and unencumbered software released into the public domain.

Anyone is free to copy, modify, publish, use, compile, sell, or
distribute this software, either in source code form or as a compiled
binary, for any purpose, commercial or non-commercial, and by any
means.

In jurisdictions that recognize copyright laws, the author or authors
of this software dedicate any and all copyright interest in the
software to the public domain. We make this dedication for the benefit
of the public at large and to the detriment of our heirs and
successors. We intend this dedication to be an overt act of
relinquishment in perpetuity of all present and future rights to this
software under copyright law.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.

For more information, please refer to <http://unlicense.org/>

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The disk image included in the distribution contains boot code which is
part of the ESDOS ][ disk format.  This is most likely copyrighted material
and therefore NOT in the public domain.  However, it is difficult to imagine
that its authors object to this code being redistributed for non-commercial
purposes, especially given its function.  ESDOS ][-formatted disk images
have been available for download on the Internet for years now with, it would
seem, no controversy at all.  (But don't go reverse-engineering it or trying
to sell it, as that's likely not what its authors had in mind.)

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The contributed Befunge-93 example sources included on the disk image
are copyrighted works made by their respective authors.  They are not
open-source or in the public domain, but their contributors' willingness to
allow them to be included in this distribution implies that they are all
freely redistributable unmodified for non-commercial purposes.  If you wish
to base your next best-selling novel on one of them, you should seek out and
contact its author for permission first.