Sustainability is an important aspect of digital library initiatives. Partly because they are often funded by grant or special monies, out of the mainstream of business as usual. For this reason, it is not surprising to see how much attention the topic has received.
Before coming to OCLC I worked for JISC in the UK. JISC provides shared services to UK higher and further education. An important part of this is its support for applied R&D in universities and colleges through its grant programmes. You can get a sense of the breadth and diversity of these programmes on the website.
You will also find guidance for what is called Exit and sustainability plans in the project management area of the site along with this note:
You must develop an exit/sustainability plan on what should happen to project outputs at the end of the project, and to explore which ones should be sustained further and how.
Another example of such attention is provided by the work of Ithaka S+R on Sustainability and revenue models for online academic resources. I discussed this in a previous blog entry: Entrepreneurial skills are not given out with grant letters. I noted one of the themes of the report as follows:
Third was the acknowledgement that projects may not naturally think of 'value' in business or commercial terms, and indeed there may sometimes be an antipathy to commercial enterprise. (This is not the only measure of 'value'.) [ Entrepreneurial skills are not given out with grant letters]
I was reminded of this a while ago when somebody resisted the use of the expression 'business model' in a conversation about the 'sustainability' of a resource on the grounds that it was not a commercial or business activity. I suppose that an important part of this is resistance to the idea that financial metrics are the only measure of value.
That said, sustainability involves securing enough revenues to continue to operate, whatever type of organization is involved.
Turning to Wikipedia, I was quite surprised at how much emphasis the entry on business models put on profit. It usefully points to a working paper providing an literature review: The business model, theoretical roots, recent developments and future research [PDF]. Interestingly, this paper shows that the term business model really only became popular in the mid-1990s, perhaps influenced by the search for new business models in an Internet environment. They also note a lot of variety in definition.
Anyway, all of this is by way of introduction to a modest statement: it seems to me to be reasonable to say that 'sustainability' involves developing a viable business model.