MasterEffect can be downloaded from
here
but it is discontinued as most, if not all shaders are incorporated into the ReShade Framework (which is integrated in the main download of ReShade).
Same goes for SweetFX, it can be accessed via the secondary download option of ReShade but its shaders are also integrated in the Framework.
The advantage of SweetFX alone over the Framework is that it is easy to configure and very lightweight, the advantage of MasterEffect alone is that it's also easy to configure and has advanced efects such as SSAO and DOF but for the general use, the Framework is the best choice as it has much, MUCH more effects besides the SweetFX/MasterEffect ones and you have some features you cannot do on SweetFX or MasterEffect such as a config tool, shader execution order, profiles and much more.