@Koh,
NAV Web Client is only for NAV 2013 & NAV 2013 R2 (NAV Framework is needed).
you can build a web custom application based (or windows application) on htlm, aspx, php etc. and consume standard NAV Web Services
ex: we have a custom web application to manage logistics&inventory written on ASPNET (that consume NAV Web Services publishing standard & custom NAV pages & codeunits)
you can find also an external nav module integration ex: "MobileNAV" or Others (search on internet)