...
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
...
They did, under the condition that "above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software."
If oh-my-fish didn't include the copyright notice and permission notice for wahoo's code they were using, then this is a valid use of the DMCA.
MIT doesn't mean you're free to use with abandon. You still have to credit and provide the license.
(Due to the DCMA takedown, I can't see whether they honoured the MIT copyright condition.)
https://github.com/wa/wahoo/blob/master/LICENSE
... Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. ...