Looking at the last two sentences in part A of the Steam Subscriber Agreement:
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The Software is licensed, not sold. Your license confers no title or ownership in the Software. To make use of the Software, you must have a Steam Account and you may be required to be running the Steam client and maintaining a connection to the Internet.
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Read that multiple times and it seems that termination of a Steam account not only locks one out of downloads but also strips your license to legally use anything previously downloaded...DRM free or not.
ALL software is licensed, whether it's bought from Steam, GOG or a retail disk.
Maybe you should also read GOG's EULA:
1.License. Company grants you a non-exclusive, non-transferable license to use the Program, but retains all property rights in the Program and all copies thereof. This Program is licensed, not sold, for your personal, non-commercial use. Your license confers no title or ownership in this Program and should not be construed as any sale of any rights in this Program. You may not transfer, distribute, rent, sub-license, or lease the Program or documentation, except as provided herein; alter, modify, or adapt the Program or documentation, or portions thereof including, but not limited to, translation, decompiling or disassembling. You agree not to modify or attempt to reverse engineer, decompile, or disassemble the Program, except and only to the extent that such activity is expressly permitted under applicable law notwithstanding this limitation. All rights not expressly granted under this Agreement are reserved by Company.
And GOG's TOS:
Termination
These Terms of Use are effective until terminated. You agree that GOG may terminate your log in access to the Service, including your user name and password, at any time for any reason without prior notice or liability. GOG may change, suspend, or discontinue all or any aspect of the Service at any time, including the availability of any feature, without prior notice or liability.
