The link provided is to a site for an Association of companies using 61508. IEC 61508 is is the international standard for electrical, electronic and programmable electronic safety related systems. It sets out the requirements for ensuring that systems are designed, implemented, operated and maintained to provide the required safety integrity level (SIL). Four SILs are defined according to the risks involved in the system application, with SIL4 being used to protect against the highest risks. The standard specifies a process that can be followed by all links in the supply chain so that information about the system can be communicated using common terminology and system parameters.
Part 3 of 61508 focused on software. This standard is not specific to the Medical Device or Health IT industries and can be a bit prescriptive in terms of process requirements, more so then medical device regulations or some related standards.