——————————
Copyright (c) 2016 Alex Hultman and contributors
This software is provided 'as-is', without any express or implied warranty. In no event will the authors be held liable for any damages arising from the use of this software.
Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions:
1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgement in the product documentation would be appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
——————————
a) This software is provided ‘as-is’, and as the author, you are not liable for damages if someone uses your library for something crazy.
b) Anyone can freely use it, for any purpose, with following restrictions:
1. “If you use this software in a product, an acknowledgement in the product documentation would be appreciated but is not required.”. They decided not to acknowledge the use of your library. You explicitly said this is OK.
2. Altered source code -> probably not.. it’s a web socket handling library.
3. This notice may not be removed. They have probably not removed it from their source code, given they distribute a binary.
edit: Found it, uws.js in resources/bootstrap/discord_rpc.zip
edit2: This is arguably worse, but the argument may be "it's a compiled binary":
-bash-4.1$ strings discord_rpc.node | grep uws.*cpp$
../../discord_common/native/third_party/uws/nodejs/addon.cpp
../../discord_common/native/third_party/uws/nodejs/addon.cpp
../../discord_common/native/third_party/uws/src/EventSystem.cpp
../../discord_common/native/third_party/uws/src/Extensions.cpp
../../discord_common/native/third_party/uws/src/HTTPSocket.cpp
../../discord_common/native/third_party/uws/src/Network.cpp
../../discord_common/native/third_party/uws/src/Server.cpp
../../discord_common/native/third_party/uws/src/UTF8.cpp
../../discord_common/native/third_party/uws/src/WebSocket.cpp
../../discord_common/native/third_party/uws/nodejs/addon.cpp
../../discord_common/native/third_party/uws/src/HTTPSocket.cpp
../../discord_common/native/third_party/uws/src/WebSocket.cpp
../../discord_common/native/third_party/uws/src/EventSystem.cpp
../../discord_common/native/third_party/uws/src/Extensions.cpp
../../discord_common/native/third_party/uws/src/Network.cpp
../../discord_common/native/third_party/uws/src/Server.cpp
../../discord_common/native/third_party/uws/src/UTF8.cpp
-bash-4.1$discord_rpc.node is an ELF file. It's hard to see how that would not be considered a binary distribution (if it was that file alone, and not being distributed with source files)
If they are not distributing source code ("3. This notice may not be removed or altered from any source distribution."), it frankly does not matter if they disclose whether they use your library or not. And if they were distributing source code, the notice would just have to stay visible in the distributed source file. An average user wouldn't be able to find that anyway.
A compiled binary != distributing source code.
As a library user under the license you used, there is no legal obligation to include the actual license in (the documentation of) your app. If you wanted that, you should have included that in the license header of your source code. Sorry to break it to you, but they're probably not doing anything wrong here.
https://dl.discordapp.net/apps/linux/0.0.1/discord-0.0.1.tar...
expand that out, then navigate to: resources/bootstrap/
expand out: discord_rpc.zip
note the presence of uws.js which is the source code for this library.
Thus this is a distribution of this library as source, not binary.
Just to be clear, I'm not the original author, and thus have no ability to enforce copyrights for this library. Just someone who doesn't like the easy stuff of license/attribution being thrown away.