The reference font for SMuFL is Bravura, an OpenType font released under the SIL Open Font License that can be downloaded from the SMuFL web site. The example glyphs in this document are all taken from Bravura.
Other SMuFL-compliant fonts are available under a variety of licenses. A list of such fonts can be found here.
Support for SMuFL-compliant fonts has been implemented by a variety of applications. A list of applications that support SMuFL can be found here.