I needed the SDK to automate some stuff in the Skype for Business 2016 client. I discovered that there is no SDK for Skype for Business 2016 and when I tried to install the Lync 2013 SDK I got this error message:
Microsoft Lync 2013 not found. I Googled this and found out that you needed to first install Lync 2013 and then the SDK. After that you could upgrade to Skype for Business 2016. I did not have time for this so I tried my own workarounds. Fortunately, I found one very quickly. If you extract the Lyncsdk.exe file with 7-zip (or any other uncompressing tool) you will see that it contains two .msi files and a .cat file.
If you just install the lyncsdk86.msi directly it will not check if you have Lync 2013 installed and you will be successful. Hope you liked this tip.