Observed Signal · Aug 25, 2026 · M&A - Announced · Source: Trending Topics · Impact: 2/5 · Sentiment: Positive
M&A Market: BOOKR Kids Raises €6.1M Series A; Callstack Acquires Margelo
Budapest-based educational technology company BOOKR Kids has secured €6.1 million in a Series A funding round led by TCEE Fund IV, advised by 3TS Capital Partners. The capital will support international expansion of its digital language-learning library and AI-enabled teacher tools. Concurrently, Polish software developer Callstack has acquired Vienna-based mobile engineering firm Margelo, a specialist in React Native open-source libraries, in a deal valuing Margelo at over €20 million. Founder Marc Rousavy will remain with Callstack to drive mobile technology developments.
An edtech growth round and a substantial app-development software agency acquisition reflect healthy funding environments for European tech infrastructure and engineering services.
Key Takeaways & Evidence Grounding
- BOOKR Kids secured €6.1 million in a Series A round led by TCEE Fund IV.
- BOOKR Kids reports revenues of approximately $2.7 million for 2025 and is EBITDA-positive.
- Polish software development company Callstack acquired Vienna-based mobile engineering firm Margelo.
- The acquisition deal values Margelo at over €20 million, with founder Marc Rousavy remaining as a key shareholder.
Connected Companies & Entities
9 Entities mappedMeta
Consumer internet platforms monetised through advertising, apps, subscriptions and VR.
“Callstack was founded in 2016 in Wrocław, a few months after Meta released React Native....”
VSCO
Photography platform combining editing, business software, creator hiring and advertising.
“Margelo lists Discord, Coinbase, Expensify, MetaMask, Rainbow, VSCO and WalletConnect among its references......”
Viking Global
Global investment firm managing public, private, credit and structured-capital strategies.
“Its finances got a boost last summer, when US fund Viking Global Investors came in with a growth investment that valued Callstack at roughly...”
Coinbase
Digital asset exchange, custody and crypto infrastructure platform.
“Margelo lists Discord, Coinbase, Expensify, MetaMask, Rainbow, VSCO and WalletConnect among its references......”
Expensify
Expense, spend, card and travel management software for businesses.
“Margelo lists Discord, Coinbase, Expensify, MetaMask, Rainbow, VSCO and WalletConnect among its references......”
Margelo
React Native mobile engineering and product design agency.
“Polish software company Callstack is acquiring Vienna-based engineering firm Margelo....”
Discord
Community chat platform with subscriptions, digital goods and native ads.
“Margelo lists Discord, Coinbase, Expensify, MetaMask, Rainbow, VSCO and WalletConnect among its references......”
3TS Capital Partners
Central European technology investor and fund adviser.
“The round is led by TCEE Fund IV, which is advised by 3TS Capital Partners....”
Callstack
Enterprise React Native engineering and AI delivery services.
“Polish software company Callstack is acquiring Vienna-based engineering firm Margelo....”
Ontology Mapping & Concepts
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