The following files are (with slight modifications for Rockbox) from dietlibc
version 0.31 which is licensed under the GPL version 2:

    gmtime.c
    strcspn.c
    strftime.c
    strncat.c
    strpbrk.c
    strtol.c
    strtoul.c
    strstr.c

The malloc routine is Doug Lea's malloc with the following license:

  Version 2.8.3 Thu Sep 22 11:16:15 2005  Doug Lea  (dl at gee)

  This is a version (aka dlmalloc) of malloc/free/realloc written by
  Doug Lea and released to the public domain, as explained at
  http://creativecommons.org/licenses/publicdomain.  Send questions,
  comments, complaints, performance data, etc to dl@cs.oswego.edu