Key Takeaway : Crypto-currencies not being a legal tender only means that you cannot use it to buy stuff but can keep it as a valuable investment just as Gold.
Crypto-currencies such as Bitcoins and likes of it made it to the headlines quite a few times in 2017, all thanks to the unprecedented surge of almost 2000% in the value of a Bitcoin at the end of the calendar year. The Government of India and Security Exchange Board of India (SEBI) issued multiple warnings against investment in crypto-currencies, as the creation, trading or use of any crypto-currency is not authorized by any central bank or monetary authority. The transactions happening in crypto-currencies all around the world are being guarded by the Blockchain Technology.
However, even after issuing consistent warnings and passing statements in the parliament, the goverment has not issued an outright ban over the use of crypto-currencies but has however been seen stressing over the crypto-currencies not being a 'lawful legal tender in India'. This statement doesn't immediately render these currencies as illegal in India.
In the budget speech by Hon. Finance Minister Mr. Arun Jaitley on 01/02/2018 he mentioned that, "Distributed ledger system or the block chain technology allows organization of any chain of records or transactions without the need of intermediaries. The Government does not consider crypto-currencies legal tender or coin and will take all measures to eliminate use of these crypto-assets in financing illegitimate activities or as part of the payment system. The Government will explore use of block chain technology proactively for ushering in digital economy."
This necessarily means that the virtual currency used for funding illegitimate transactions will be investigated. It is also clear that the government is interested in exploring what the distributed ledger system or the block chain technology has to offer. However given the complexity and enormity of the Blockchain system, it is safe to consider that there is still time till government figures out what it actually is and what potential does it carry.
Crypto-currencies not being a legal tender only means that you cannot use it to buy stuff but can keep it as a valuable investment just as Gold.