Without a license, this code cannot be reused in or adapted for other packages which have an open source license.
If you want the maximum reuse of your code (which also helps with citations if you care about that), please use an MIT license. This is consistent with the Matlab file exchange default, and also with the whole Python ecosystem. See http://choosealicense.com/ for tradeoffs of the most common licenses.
Without a license, this code cannot be reused in or adapted for other packages which have an open source license.
If you want the maximum reuse of your code (which also helps with citations if you care about that), please use an MIT license. This is consistent with the Matlab file exchange default, and also with the whole Python ecosystem. See http://choosealicense.com/ for tradeoffs of the most common licenses.